Abstract:

Provided is a composition comprising (a) at least one halogenated compound
selected from the group consisting of C3-C5 hydrofluoroolefin,
CF3I, and combinations thereof, and (b) an effective stabilizing
amount of a sesquiterpene selected from the group consisting of farnesol,
farnesene, and mixtures thereof.

Claims:

1. A composition comprising:a. at least one halogenated compound selected
from the group consisting of C3-C5 hydrofluoroolefin,
CF3I, and combinations thereof;b. an effective stabilizing amount of
a sesquiterpene selected from the group consisting of farnesol,
farnesene, and mixtures thereof.

2. The composition of claim 1 wherein said halogenated compound is
selected from the group consisting of HFO-1234yf, HFO-1234ze, CF3I,
and combinations thereof.

3. The composition of claim 1 wherein said sesquiterpene is present in an
amount of about 0.001 weight percent to about 10 weight percent based on
the total weight of the composition.

4. The composition of claim 1 wherein said sesquiterpene is present in an
amount of about 0.1 weight percent to about 5 weight percent based on the
total weight of the composition.

5. The composition of claim 1 consisting essentially of about 95 to about
99.9 weight percent HFO-1234yf and about 0.1 to about 5 weight percent
farnesol.

6. The composition of claim 1 consisting essentially of about 99 to about
99.7 weight percent HFO-1234yf and about 0.3 to about 1 weight percent
farnesol.

7. The composition of claim 1 consisting essentially of about 95 to about
99.9 weight percent HFO-1234yf and about 0.1 to about 5 weight percent
farnesene.

8. The composition of claim 1 consisting essentially of about 99 to about
99.7 weight percent HFO-1234yf and about 0.3 to about 1 weight percent
farnesene.

9. The composition of claim 1 consisting essentially of about 99 to about
99.7 weight percent HFO-1234ze and about 0.3 to about 1 weight percent
farnesol.

10. The composition of claim 1 consisting essentially of about 99 to about
99.7 weight percent CF3I and about 0.3 to about 1 weight percent
farnesol.

11. The composition of claim 1 consisting essentially of about 90 to about
99.9 weight percent of a mixture of HFO-1234yf and CF3I and about
0.1 to about 10 weight percent farnesol.

12. The composition of claim 11 wherein said mixture consists essentially
of about 65 to about 75 weight percent HFO-1234yf and about 25 to about
35 weight percent CF3I.

13. The composition of claim 1 further comprising a polyalkylene glycol
lubricant suitable for use in a refrigeration system.

14. The composition of claim 1 having a temperature of greater than about
50.degree. C.

15. A method for chemically stabilizing a refrigerant composition
comprising:a. mixing a refrigerant selected from the group consisting of
HFO-1234yf, HFO-1234ze, CF3I, and combinations thereof, with an
effective stabilizing amount of a sesquiterpene selected from the group
consisting of farnesol, farnesene, and mixtures thereof.

16. The method of claim 18 wherein said refrigerant further comprises a
polyalkylene glycol lubricant suitable for a refrigeration system.

17. A method for stabilizing a solvent comprising:a. mixing a solvent
comprising at least one halogenated compound selected from the group
consisting of C3-C5 hydrofluoroolefin, CF3I, and
combinations thereof, with an effective stabilizing amount of a
sesquiterpene selected from the group consisting of farnesol, farnesene,
and mixtures thereof; andb. increasing the temperature of the solvent to
at least 50.degree. C.

Description:

BACKGROUND

[0001]1. Field of Invention

[0002]This invention relates to a composition comprising at least one
halogenated organic compound and a stabilizer. More particularly, the
invention relates to a composition comprising a hydrofluoroolefin and a
stabilizer.

[0003]2. Description of Related Art

[0004]Fluoroolefins and certain other compounds, such as CF3I, have
been proposed as replacements of chlorofluorocarbons,
hydrochlorofluorocarbons, and hydrofluorocarbons which, conventionally,
have been used as working fluids, refrigerants, solvents, blowing agents,
and the like. Fluoroolefins and CF3I are characterized as having a
low global warming potential (GWP) and little or no ozone depletion
effect and, thus, are more environmentally friendly compared to
chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons.
Moreover, fluoroolefins and CF3I have excellent refrigeration
performance and generally are nontoxic and nonflammable.

[0005]The refrigerant's low global warming is due, in part, to the fact
that these compounds are less chemically and thermally stable than their
predecessor refrigerants. More particularly, fluids that have low GWP
values typically have a reactive site, such an alkene's double bond, that
advantageously increases the rate of decomposition in the atmosphere thus
producing a short atmospheric lifetime. This reactive site in the
molecule is usually not reactive enough to cause the substance to be so
unstable that it's utility as a refrigerant or solvent in degraded. While
these properties are typically maintained at low temperatures, the
stability of low GWP refrigerants and solvents is jeopardized when they
contact with conventional materials of construction of refrigeration
systems at high temperatures (e.g., ≧50° C.).

[0006]It is also possible that the reactive sites of the low GWP materials
can be the source of reaction during use and also during storage.
Reactions such as polymerization or decomposition have been seen when
some of these low GWP substances have been stored under extreme
conditions. Even though many of these low GWP materials are fairly stable
during use, they are measurably less stable than the long lived
hydrofluorocarbons they replace.

[0007]In substituting low GWP substances which have this necessary
reactive site in the molecule, there is a need to stabilize the fluid
during storage and use if the fluid is subjected to extreme temperatures
or long storage times. While conventional stabilizers for low GWP working
fluids are often soluble in conventional lubricating oil, they are not
soluble in the refrigerant itself. A stabilizer that is soluble in the
refrigerant, and more preferably soluble in both the refrigerant and
lubricant, would be advantageous.

SUMMARY OF THE INVENTION

[0008]Applicants have discovered that the addition of a sesquiterpene,
preferably farnesol and/or farnesene, to a composition comprising one or
more low GWP compounds, particularly trifluoroiodomethane (CF3I),
C3-C5 fluoroolefins, and combinations thereof, increases the
chemical stability of the composition at high temperatures. More
particularly, farnesol acts as radical scavenger in a composition
comprising a combination of a stabilizer comprising farnesol and/or
farnsene and a low GWP compound. For example, farnesol can slows the
polymerization of HFO-1234yf and can slow the decomposition of CF3I
to form R-23. Farnesol also slows the polymerization of polyalkylene
glycol compressor lubricant. Moreover, farnesol andfarnsene can be added
directly to the refrigerant of a refrigeration system which facilitates
its uniform distribution since the refrigerant has a low viscosity
compared to conventional refrigeration system lubricants.

[0009]Accordingly, an aspect of the invention is a composition comprising
(a) at least one halogenated compound selected from the group consisting
of C3-C5 hydrofluoroolefin, CF3I, and combinations
thereof; and (b) an effective stabilizing amount of a sesquiterpene
selected from the group consisting of farnesol, farnesene, and mixtures
thereof. Preferred C3-C5 hydrofluoroolefins include
tetrafluoropropenes, particularly 2,3,3,3-tetrafluoro-1-propene
(HFO-1234yf) and 1,3,3,3-tetrafluoro-1-propene (HFO-1234ze).

[0010]According to another aspect of the invention, provided is a method
for chemically stabilizing a refrigerant composition comprising mixing a
refrigerant selected from the group consisting of HFO-1234yf, HFO-1234ze,
CF3I, and combinations thereof, with an effective stabilizing amount
of a sesquiterpene selected from the group consisting of farnesol,
farnesene, and mixtures thereof.

[0011]According to yet another aspect of the invention, provide is a
method for stabilizing a solvent comprising (a) mixing a solvent
comprising at least one halogenated compound selected from the group
consisting of C3-C5 hydrofluoroolefin, CF3I, and
combinations thereof, with an effective stabilizing amount of a
sesquiterpene selected from the group consisting of farnesol, farnsene,
and mixtures thereof; and (b) increasing the temperature of the solvent
to at least 50° C.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0012]The present invention provides a composition comprising at least one
low GWP, and an effective amount of a sesquiterpene stabilizer,
preferably farnesol and/or farnsene. These compositions are particularly
useful as solvents and/or refrigerants at high temperatures, but can also
be used as blowing agents, aerosol propellants, fire extinguishants, and
sterilants. As a refrigerant, the composition can be used as a heat
transfer medium in refrigeration systems, refrigerators, air conditioning
systems, heat pumps, chillers, and the like.

[0013]As used herein, the term "low GWP" refers to fluids that have a GWP
of less than 500 relative to carbon dioxide. Preferably, they are fluids
that have GWP values of less than 400. More preferably they have a GWP of
200 or less.

[0014]As used herein, the term "stabilizer" refers to inhibitor,
stabilizers, scavengers. Such stabilizers mitigate chemical and/or
thermal degradation of the stabilized compound and/or polymerization of
the stabilized compound, particularly at temperatures at or above
50° C. and/or when the compound is stored for at least about 3
month, more preferably at least about 6 months, and even more preferably
at least about 1 year.

[0015]As used herein, the term "effective amount" refers to an amount of
stabilizer of the present invention which, when added to a composition
comprising at least one fluoroolefin, results in a composition that will
not degrade to produce as great a reduction in refrigeration performance
when in use in a cooling apparatus as compared to the composition without
stabilizer under similar storage and/or temperature conditions. Such
effective amounts of stabilizer may be determined by way of testing under
the conditions of standard test ASHRAE 97-2004. In a certain embodiment
of the present invention, an effective amount may be said to be that
amount of stabilizer that when combined with a composition comprising at
least one fluoroolefin allows a cooling apparatus utilizing said
composition comprising at least one fluoroolefin to perform at the same
level of refrigeration performance and cooling capacity as if a
composition comprising 1,1,1,2-tetrafluoroethane (R-134a), or other
standard refrigerant (R-12, R-22, R-502, R-507A, R-508, R401A, R401B,
R402A, R402B, R408, R-410A, R-404A, R407C, R-413A, R-417A, R-422A,
R-422B, R-422C, R-422D, R-423, R-114, R-11, R-113, R-123, R-124, R236fa,
or R-245fa) depending upon what refrigerant may have been used in a
similar system in the past, were being utilized as the working fluid.

[0017]The term "farnesol" is the compound
3,7,11-trimethyl-2,6,10-dodecatrien-1-ol, including any and all
stereoisomers thereof. Farnesol is a natural organic compound which is a
sesquiterpene alcohol found as a colorless liquid and is insoluble in
water, but miscible with oils. It has the chemical structure:

##STR00001##

[0018]The term "farnesene" includes α-farnesene (i.e.,
3,7,11-trimethyldocecadodeca-1,3,6,19-tetraene) and β-farnesene
(i.e., 7,11-dimethyl-3-methylene-1,6,10-dodecatriene), including any and
all stereoisomers thereof.

[0020]HFO-1234yf, HFO-1234ze, HFO-1233zd, and CF3I are commercially
available compounds and also can be synthesized by known methods.

[0021]Certain embodiments include effective amounts of stabilizer for use
in the present invention that comprise from about 0.001 weight percent to
about 10 weight percent, more preferably from about 0.01 weight percent
to about 5 weight percent, even more preferably from about 0.3 weight
percent to about 4 weight percent and even more preferably from about 0.3
weight percent to about 1 weight percent based on the total weight of
compositions comprising at least one fluoroolefin as described herein.
When a mixture of stabilizers or stabilizer blend is used, the total
amount of the mixture or stabilizer blend may be present in the
concentrations as described herein above.

[0022]Stabilizers can be introduced into the HFO-1234yf, HFO-1234ze,
and/or CF3I refrigerant by various means at different points during
manufacture of the refrigerant or later once the refrigerant has been
charged to an air-conditioning system. Stabilizer can be added by in-line
injection using metering valves and mass flow meters to meter in a
pre-determined amount of stabilizer. In such fashion, stabilizer could be
added during product blending or product packaging. Alternatively,
stabilizer can be pumped into a blending tank containing the refrigerant.
Load cells would facilitate addition of stabilizer to the proper amount
by weight difference. Stabilizer may also be added to refrigerant by
using density versus temperature data to convert the desired weight of
stabilizer to a volume. The required volume of stabilizer could then be
pumped or fed by gravity to the refrigerant blend tank.

[0023]Farnesol is soluble, for example, at up to 10% in 70% 1234yf/30%
CF3I. In cases where solubility of the stabilizer in one or both of
the refrigerant components is inadequate, a small amount of another
component such as compressor lubricant in which the stabilizer is
soluble, can be added to increase the solubility of the stabilizer in the
resulting matrix.

[0024]Composition comprising one or more low-GWP compounds and a
stabilizing amount of farnesol and/or farnsene are characterized by a
significant improvement in chemical stability at a temperature of about
50° C. and higher, particularly about 100° C. and higher,
and more particularly about 200° C. and higher, compared to the
low-GWP compounds without farnesol. Under these conditions, the low-GWP
compounds demonstrated a significant reduction in thermal or chemical
degradation, particularly polymerization and particularly with respect to
reactions occurring at an olefinic double bond.

[0025]Once the stabilized refrigerant is charged to a system, prolonged
system operation may result in decline of the effectiveness or
availability of stabilizer. A system leak or system servicing may result
in loss of lubricant. This too, diminishes the amount of stabilizer
available in the system. The stabilizer shortfall can be made up by
adding concentrated stabilizer in refrigerant if the refrigerant has
leaked out. Small cans of stabilizer concentrate in refrigerant equipped
with appropriate fittings, valves, and hose can be used to transfer
stabilized refrigerant into the system. Likewise, the shortfall can be
made up by adding concentrated stabilizer in oil if oil has leaked out.
In-line stabilized oil capsules with compatible fittings for connection
to standard service gauge sets can be used. If refrigerant and oil have
both leaked out, the contents of such stabilized oil capsules can be
pushed into the system using refrigerant. Manual oil injector pumps can
be used to introduce make-up stabilized oil.

[0026]When it is determined that additional stabilizer needs to be added
to a charged system and the full complement of refrigerant and oil are
present in the system, a refrigerant recovery/recycle unit equipped with
a stabilizer concentrate reservoir can be used to add stabilizer to the
refrigerant. The refrigerant would be recovered using a vapor-recovery
mode recovery unit. Any entrained oil would be stripped out in an oil
separator. Refrigerant would be compressed, condensed, and filtered.
Liquid refrigerant would then pass through an in-line vessel containing
stabilizer. The stabilizer would be dissolved by the circulating
refrigerant. As necessary, re-circulation of the refrigerant through the
stabilizer-containing vessel could be conducted until the necessary
amount of stabilizer is dissolved in the refrigerant. Using a sensing
means such as refractive index, the circulation/re-circulation would be
controlled. Once the proper amount of stabilizer was in solution, the
recovery/recycle unit would dispense the stabilized refrigerant back into
the A/C system. Other means to introduce stabilizer concentrate into
recovered refrigerant within a recovery/recycle unit would include
metering from a concentrate reservoir into a stream of circulating
refrigerant or metering into the refrigerant recovery tank. The driver
could be a fluid pump, a weep hole between the stabilizer concentrate
reservoir and recirculating refrigerant, gravity feed, or any means to
create a pressure differential such as the circulating refrigerant or a
temperature difference. The temperature difference can be attained by
employing heat as from an electric heating element or by cooling as from
expansion of at least some portion of the refrigerant in the
recovery/recycle unit.

[0027]Another means to deliver stabilizer(s) to a system already
containing a full charge of refrigerant and lubricant is to incorporate
the stabilizer(s) into a small in-line vessel. The vessel could be a
separate vessel or the stabilizer(s) could be incorporated into a
filter/drier design. Filter/driers are already used in air-conditioning
and refrigeration systems. The stabilizer(s) could be delivered to the
system en total or the vessel could contain a support or media that would
provide release of stabilizer(s) over time.

[0028]Refrigerant/lubricant stabilizers that are soluble in compressor
lubricant can be introduced into the lubricant by various means at
different points during manufacture of the refrigerant or later once the
refrigerant has been charged to an air-conditioning system. Stabilizer
can be added by in-line injection using metering valves and mass flow
meters to meter in a pre-determined amount of stabilizer. In such
fashion, stabilizer could be added during product blending or product
packaging. Alternatively, stabilizer can be pumped into a blending tank
containing the lubricant. Load cells would facilitate addition of
stabilizer to the proper amount by weight difference. Stabilizer may also
be added to lubricant by using density versus temperature data to convert
the desired weight of stabilizer to a volume. The required volume of
stabilizer could then be pumped or fed by gravity to the lubricant blend
tank.

[0029]Compatible materials of construction are required for recovery,
recycle, and reclamation of refrigerants such as HFOs and azeotropes and
blends of HFOs with other desirable refrigerant components. Low GWP
refrigerants such as 1234yf/CF3I have solubility characteristics
that differ from CFCs, HCFCs, and HFCs of the past. Metals, plastics, and
elastomers that constitute refrigerant wetted parts must be compatible
with the refrigerant. CF3I can react with metals. Passive metals,
whether elemental, alloyed, or chemically treated (electrolytic
processes, chemical conversion processes, or surface active chemicals)
can be used to produce compatible metals for use in refrigerant service
equipment such as recovery/recycle machines or reclamation units.